Question
• Why are some chemicals in a solution visible under one type
of light but not another?
Purpose
• The purpose of our project was to extend the simple test of
Chromatography and examine the paper in a different
electromagnetic wave (ultraviolent light) rather than visible
light.
Hypothesis
• If we use a Black light (UV) to examine the ink components,
then we will encounter more components than with white
light.
Materials
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Filter paper; enough to make eighteen 2 x 7 cm strips
Scissors
Pencil
Ruler; metric
Wooden coffee stirrer or other similar wooden splint
150 mL beaker
Isopropyl alcohol
Water
400 mL beaker
Plastic wrap
Mini binder clips (2)
Black pens or markers (3). Choose three different black pens and markers.
Lab notebook
Procedure
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1. Cut the filter paper into strips approximately 2 centimeters (cm) wide by 7 cm long. You will need a total of 18 chromatography strips.
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2. Take one of the chromatography strips and use a ruler and pencil to draw a line across it horizontally 1 cm from the bottom.
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3. Using one of the pens/markers, place a small dot of ink at the center of the origin line of a chromatography strip. a. Use a pencil to label which
pen/marker you spotted on the chromatography strip. Repeat this step until you have spotted ink on 6 chromatography strips for each pen/marker.
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4. Pour 20 milliliters (mL) of isopropyl alcohol into the 150 mL beaker. Add 20 mL of water to the beaker so that the final volume is 40 mL. Stir
thoroughly with the wooden splint.
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5. Pour the solution into the 400 mL beaker. Cover the beaker with plastic wrap, so that the solution does not evaporate. This is your solvent.
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6. Pour a small amount of the solvent back into the 150 mL beaker. a.Clip two of the prepared chromatography strips to a wooden splint. Make sure
the two strips do not touch each other and the bottoms align. Rest the splint on top of the beaker so that the strips hang into the jar. If necessary, add
more solvent to the small beaker. The goal is to have the end of the chromatography strip just touching the surface of the solvent solution as shown in
Figure 4 below. Add solvent as needed to achieve this goal.
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7. Cover the top of the beaker with plastic wrap.
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8. Set aside the remainder of the unused solvent (covered with a lid or plastic wrap) for additional runs.
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6.Let the solvent rise up the strip (by capillary action) until it is about 0.5 cm from the top, then remove the strip from the solvent. Keep a close eye on
your chromatography strip and the solvent front — if you let it run too long the dye may run off the paper and become distorted.
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7.Use a pencil to mark how far the solvent rose.
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8.Allow the chromatography strip to dry, then measure (in centimeters) and calculate the Rf value for each pen/marker dye component. Record your
results in your lab notebook.
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9.Repeat steps 5 - 8 until you have run all of the chromatography strips.
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10.Using the five repeated strips for each pen/marker, calculate the average Rf for each dye component.
Variables
• Independent Variable: The type of Light (Visible or Ultraviolet)
• Dependent Variable: The distance traveled by the Ink components
• Constant: The objects being tested
White Light
Crayola
Marker
Data/Results
Sharpie
Ballpoint Pen
Crayola
Marker
Black Light
Sharpie
Ballpoint Pen
1. Sample:
4.5 cm
3 cm
2.5 cm
1. Sample:
4.5 cm
2.5 cm
3 cm
Solvent:
4.5 cm
4.5 cm
5.25 cm
Solvent:
4.5 cm
5.25 cm
5.25 cm
Rf value:
1
.66
.48
Rf value:
1
.48
.57
2. Sample:
5 cm
2.5 cm
2.5 cm
2. Sample:
4.5 cm
3 cm
2 cm
Solvent
5 cm
5 cm
5 cm
Solvent
4.5 cm
5 cm
5 cm
Rf value
1
.5
.5
Rf value
1
.6
.4
3. Sample:
4.5 cm
2.5 cm
2.5 cm
3. Sample:
5
3 cm
2.5 cm
Solvent:
4.5 cm
4.5 cm
5.25 cm
Solvent:
5
4.75 cm
5 cm
Rf value:
1
.55
.48
Rf value:
1
.63
.5
Conclusion
• In this experiment I learned that my hypothesis was incorrect because
Black light does not change the ink components that are visible in the
solvent. In the future I will measure the strips as soon as I finish the
test so that I can see how far the solvent went and to be more precise
with my experiment.